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Goldfish are loved by everyone everywhere. They are some of the favorite choices for aquariums all over the world. Most of the Goldfish that we see in aquariums are inbred, or hybrid versions of the original Goldfish. The original goldfish are freshwater species from the family of fish called Cyprinidae. They became pet fish in ancient China due to their beautiful golden appearance. Goldfish were kept in the ponds of the Emperor’s palace. Due to the importance of goldfish, they became a center of research, and fishkeepers of that time introduced new varieties of Goldfish and that trend hasn’t slowed down since. It helped preserve the species, but it also made this species more vulnerable to diseases. There are a lot of diseases that can kill these small and beautiful creatures. All of these diseases have different symptoms that help diagnose the disease so that it can be treated. But there is one particular symptom that is often seen in many cases, and it is the change of the color of Goldfish.

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According to researchers, when goldfish change its color to black, it can be a symptom of several things that can be wrong. The three most easy explanations for this color change are as follows, disease attack, ammonia in water, and stress. But there are a lot of other reasons why this color change from golden to black happens. To treat this symptom accurately, you need a proper diagnosis of the situation at first. Otherwise, you may have been treating your fish with the wrong medication, and with the wrong method and that can result in the death of your fish. So, before going for selecting medicine or measures to cure your fish, you must start with a proper diagnosis. The article below explains why Goldfish turn black and how you can treat this or prevent this from happening.

Is It Something To Worry About?

Yes, in most cases, it is something that you should worry about. For example, if you are a new fish keeper, and you have got a goldfish, but you are not aware of the proper ways to care for your fish. Also, if your goldfish is not eating properly, or there are signs or symptoms of the disease. Then you should worry about your fish. But there are also some cases, where the black color in goldfish is normal and you don’t need to worry about it. For example, there are some varieties of goldfish that are partially or completely black. This is a genetic trait in those varieties. So, if you have one of those in your tank and it is turning black or has black color, you should not worry about it.

From the discussion above, it is clear that the answer to this question depends on the situation, which can be unique in every case. For example, if you have a fish whose body has black patches, then it is something that you can simply ignore. But if you have a Goldfish that has no genetic markers related to black color, and it is turning black, then you should worry about it. In the early days of fishkeeping, the fishkeepers didn’t know of any remedy related to this issue, and most of the time they would just leave their Goldfish in the tank until it died or they would replace it with a new one. But now, we know that certain issues can cause this problem. So, we need to treat those causes instead of leaving the Goldfish to die. The article below contains information about why Goldfish turn black. Read it carefully to know the reasons and remedies.

Reasons Why A Goldfish Turns Black?

As mentioned above, there can be several reasons behind a Goldfish turning black. From genetics to environment, and disease, anything can be a reason. Below is a list of some of the most common reasons behind this.


Genetics plays a very important role in how a species of fish looks, including Goldfish. The fishkeepers and breeders use the genetic traits of the fish while breeding. Some species of Goldfish are created with such a genetic makeup that they develop black color. In some cases, the black color is only seen as a patch on the body of the fish, but some breeds are almost completely black. So, if you have bought a Goldfish and it has black patches, or it has black color, it is better to take a look at its genetic history instead of feeding it a medicine or changing anything.

Black Goldfish is one of the best examples of this genetic phenomenon. It is a breed of Goldfish that is bred specially for its black color. It looks stunningly beautiful and is loved by the fishkeepers for its unique black color and long fins. It has all the same features as a normal Goldfish, except for the color which in this case is black. So, if you have bought one such variety of the Goldfish that has black color or patches, or if you have bred fish in your tank and it turned out to be a black goldfish, you should not worry. This coloration is permanent but causes no harm to the fish itself as it is natural and not because of any disease. Most Goldfish that have black genetic markers, start displaying the black color soon after their birth but in some varieties, this may take some time.

Blending In New Environment

When you put a fish in a new tank, you are putting it in a new environment, and Goldfish are known for being sensitive to this kind of change. So, when you take them from one aquarium, or environment and introduce them to a new environment, they react to the environment and try to blend in. There are times when you put them in a tank that has damp lighting conditions, or a biotope tank.

In these cases, your Goldfish might develop black color to blend in and mix within the new habitat. Although these types of changes are rare, they still do happen. So, if this is the case, you do not need to worry as this is also a natural process. The color change, however, can be permanent. It is not a bad thing as it won’t harm your fish, instead, it would make it more comfortable in the new blackish habitat. If you don’t want this to happen, the only thing that you can do is to make sure that you never put your fish in a blackish habitat or habitats.


The first two conditions we discussed were not the ones that affect the health of your fish, but the ones that we will discuss now are the ones you should worry about. The first one on this dangerous list is Ammonia poisoning. Ammonia poisoning happens only when the level of ammonia in your tank exceeds the recommended limits. It is a very dangerous situation as it can kill your fish. It can cause the skin of the fish to react, and change color as the health of your fish deteriorates. The higher the level of the ammonia in your tank, the darker shade of black would appear on the scales of your Goldfish.

Ammonia poisoning causes the fish scales to deteriorate, so when this poisoning ends and the body of the fish starts the recovery process. The black patches would appear all over the body of the fish. This indicates that the recovery process has started and your fish will be okay in the next few days. It may take some time but these patches will go away automatically. Black patches that are caused by ammonia poisoning are signs of recovery after poisoning and not before. It is an important factor to keep in mind.

If these patches appear on your Goldfish, you should reevaluate your care plan. You should do cleaning more often, and should also recycle the water quickly. Also, it is better to use a stronger filter as compared to the previous one as it was not doing its job properly. It is important to make sure that your fish never has to face ammonia poisoning once again. Goldfish can survive ammonia poisoning for a brief period, but prolonged exposure or repeated exposure can kill your fish. So, try to avoid such conditions in the future and your fish will never display any black patches.

Note: Black patches in this case are not caused by ammonia poisoning, instead, they are caused by the healing process. So, you don’t need to worry about them, instead, you need to worry about the type of care that you are offering your fish and the type of environment where you are keeping it.

Stress Conditions

If you are keeping the Goldfish in a very small container, or not caring for it properly, or if you are keeping it in a crowded tank, it can cause stress and depression in your Goldfish. Similar to us, fish also need a peaceful, and comfortable habitat, and when they don’t get such conditions to live, they get depressed. This depression and stress causes your fish to lose appetite, and stop eating. It can also lead to several other health issues. Black patches on Goldfish act as an indicator if your fish is under stress or not. If your fish isn’t living in the type of conditions that it needs, and it has started to develop black patches on its scales, you should make changes to the habitat and living conditions of your fish.

Make sure that these changes impact the mind of your fish. Simple changes like removing competitors, and adding fish of the same species can encourage the fish to come out of depression and be more active. These improved conditions will help your fish recover from stress conditions and that would also cause the black patches to slowly disappear. If you want your fish to never go through the depression in the future, it is very important to maintain the tank’s living conditions in the optimal range. Also, make sure that your fish tank isn’t overcrowded. Overcrowding is one of the main reasons behind the depression and stress in the fish.

You can prevent the stress caused by the overcrowding by making sure that you only put the number of fish in the tank according to recommended limits of the tank. Smaller tanks can only sustain a small number of fish, so, you will need bigger containers for more fish. Also, as the fish ages, it needs more space. So, make sure that you select a tank that has room for the growth of the fish. If the tank is smaller, it would suppress the natural growth of the fish and that can lead to stress. Apart from tank size, and tank condition, you will also have to maintain proper hygiene in your tank to prevent any kind of stress. All of these conditions directly impact the mental health of your fish, so it is better to keep them within the perfect ranges and cycles.


Diseases can also lead to Goldfish turning black. Some diseases can cause this, such as the Black Spot Disease. It is one of the rare fish diseases that attacks a lot of fish species including Goldfish. This disease causes the formation of black spots on the scales of the fish. As this disease progresses, the spots become more and more apparent. It can be lethal in some cases. If you see any signs of this disease, it is important to quarantine your fish and treat it using medication.

Apart from black spots disease, there are also a lot of other diseases that attack Goldfish. These diseases do not directly cause the Goldfish turning into black, but they work as a factor. For example, when a disease attacks the Goldfish, it puts a lot of strain on the fish. Sometimes, Goldfish can recover from this disease by itself, but that puts a lot of strain on their bodies and mental health. It can cause them to change color due to the stress of the disease that it is facing. So, if your fish is suffering from any disease and you have noticed it by the change of color, it is better to treat it right away to make sure that your fish survives.

Can This Color Change Be Reversed?

It depends on the cause of the color change. For example, if the color change was caused by the disease or ammonia poisoning, or stress then “Yes.” can be reversed. But if this color change was caused by genetics, it will not be reversible. So, before trying to look for the remedies for color reversing, it is better to research the reasons behind this color change. It would give you the idea if you can reverse this color change or not. Here are a few things that can help you with the color change reversal.

  • Genetics: if your Goldfish is black because of genetics or breed, it is not possible to change colors.
  • Ammonia Poisoning: Your fish will return to its normal color without any effort. The only thing you have to do is to properly clean your tank regularly to prevent the black color from ever coming back again.
  • Stress: It is also a reversible color change. But you will have to care for your fish in every way and make sure that it gets to live in a peaceful, and comfortable habitat with perfect conditions that are maintained properly.
  • Disease: Black spots caused by the disease may require some time to fade, but Yes, it is also a reversible condition. You will have to make sure that your fish never encounters the black spots disease or any other disease. Keeping your fish healthy will help you maintain the color of your fish.

Conclusion; What To Do If Your Goldfish Changes Color?

If your Goldfish has changed its color from its normal color, you should try to find out the reason behind this color change. The reason behind the color change will help you strategize your next move. For example, if it is because of a disease, then you will have to treat your fish with proper medication. But if this color change is genetic or because of the breeding, then you can almost do nothing about it. There are also other causes of the color change such as stress conditions and ammonia poisoning. If these are the causes behind this color change then you should clean your tank and provide your fish with a healthy, comfortable, and peaceful habitat.


Question: Are there any black Goldfish varieties?

Answer: Yes, there are many Goldfish varieties and subspecies that have black color, or black patches. One of the best examples of black-colored goldfish varieties is the Black Goldfish. It is one of the most famous Goldfish varieties that has a beautiful black-colored appearance.

Question: What to do when Goldfish turns black?

Answer: You should check the levels of ammonia in your tank. If the ammonia levels were normal, then you should check for the signs of disease. You need to know the reason behind this color change before doing anything. So, test for depression and stress, overcrowding, or food-related issues. Once you find the culprit behind this color change, you will be able to treat it and reverse the color change.

Question: How to avoid ammonia poisoning in Goldfish?

Answer: Ammonia poisoning in Goldfish causes the Goldfish to change their color to black. You can prevent this from happening by cleaning your tank and removing the ammonia from your tank. Ammonia collects in the bottom of your tank in the form of leftover food, and the excretion of your fish. Removal of ammonia would help your fish to recover and this would cause the color change to be reversed.

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